1. Field of the Invention
The present invention generally relates to a thin film transistor (TFT) array substrate and a method for fabricating the same, and more particularly, to a TFT array substrate having a photosensor, and a method for fabricating the same.
2. Description of Related Art
As science and technology being developed, great improvements have been made with respect to technologies for display devices, and accordingly the demand for display devices is drastically increasing. In the earlier days, cathode ray tube (CRT) displays presented outstanding displaying performance and mature techniques comparing with other kinds. Therefore, the CRT displays had almost exclusively occupied the display market for a very long period. However, the green concept of environmental protection has been paid with more attention, and therefore the CRT displays which consume a lot of energy and generate a large amount of radiation, and even often occupy a large 3D space, are now incapable of satisfying the new trend of display devices, (e.g., being lighter, thinner, shorter, smaller, cuter, and lower power consumption), demanded by the current market. As such, flat panel displays (FPD) which are lighter and thinner now gradually displace the position of those bulky CRT displays in the market. Specifically, liquid crystal displays (LCD), as an important representative of FPDs, having outstanding advantages such as improved imaging performance, optimal space utilization efficiency, low power consumption, and low radiation, have become a mainstream of the display market.
Recently, it has been proposed to integrate a photosensor into an FPD, in order to improve an operation convenience of a display interface between a user and the FPD, or for the purpose of improving the entire displaying quality of the FPD. Specifically, the photosensor is adapted to serve as an input apparatus of an optical touch panel, in which when a user uses his finger or other means to touch the optical touch panel, the photosensor integrated inside the LCD panel detects a variation of light and outputs a corresponding signal to execute a corresponding function or operation. In another application, the photosensor is integrated in an FPD serving as an ambient light sensor for detecting an intensity of the ambient light.
More specifically, when selecting photosensitive materials for making the photosensor, amorphous silicon material having a higher light sensitivity, (i.e., a photocurrent in an amorphous material has a larger variation range relative to a change of light intensity), will usually be more often considered. Therefore, when trying to integrate a photosensor to an amorphous silicon TFT array substrate, the amorphous silicon material is often used between two electrodes to constitute the photosensor.
However, when using the amorphous silicon material as a photosensitive material for making the photosensor, a difficulty may occur. Even when there is no voltage applied on the two electrodes over the amorphous silicon, if only the amorphous silicon material is illuminated by a light, the photosensor will be caused with a problem of photocurrent attenuation, and thus affecting the reliability of the photosensor.
As such, it is very desirable to properly design the structure and position of the photosensitive material in the photosensor, so as to achieve a higher reliability of the photosensor. Further, it is also a critical concern to compatibly integrating the process of fabricating the photosensor into the entire process of fabricating the amorphous silicon TFT.